If you have an ample data plan (most smartphones have unlimited one) for your iPhone, or you simply don't want to pay for two separate data plan, plus, you may have multiple devices to access the internet. What's the solution? You could tether your iPad to iPhone 3G network, and also other devices. What you need is only a jailbreak iPhone and one of the iPhone tethering applications introduced below.
Tethering iPad to iPhone with Pdanet (free)
Pdanet is one of the 2 best tethering software titles that turns your iPhone of any version into a WiFi HotSpot so that you can connect to internet from your computer or iPads. It allows your iPad to go online wirelessly through the 2G/3G/4G network on the iPhone. Besides WiFi tethering, you could also use a USB cable to tether iPad to iPhone 4S, iPhone 4, iPhone 3GS, iPhone 3G, and the first generation of iPhone.
Easy steps to Tether your iPad to iPhone
1.Jailbroken your iPhone.
2.Update Cydia in the jailbroken iPhone.
3.Search for Pdanet and Install.
4.Make settings in Pdanet and starting tethering iPad.
Please check your contract/carrier agreement regarding additional iPad tethering. Extra charges may apply.
Tethering iPad to iPhone with MyWi ($9.99 one-time free)
You also need to jailbreak your iPhone before using MyWi. MyWi is similar to Pdanet, but easier to use and costs you $9.99 USD. However, compared to your additional data plan, it's still a cheap solution to let your iPad connect to internet effortlessly. Below is a YouTube video tutorial to tether iPad to iPhone. Check it out.